1. Field of the Invention
The present invention relates to thermal management systems for electrical storage devices, and more particularly to thermal management systems for batteries and capacitors used for power storage in aircraft.
2. Description of Related Art
Advances in electronics and electronics functionality have led to a proliferation of power consuming devices integrated into vehicles. Modern automobiles include numerous processors to manage vehicle systems previous controlled by mechanical systems. Modern aircraft include fly-by-wire systems connecting processors and actuators in placed of hydraulic systems because of the need for additional on-board functionality and weight savings. Increase in power demand gives rise to a corresponding requirement for electrical storage devices capable of meeting this increased power demand. Of particular interest are power sources with greater power density than conventional sources, thereby being capable of supplying a greater amount of power for a given size and weight than conventional sources.
In the drive for greater power density, power sources such as batteries and capacitors have moved to increasingly energetic chemistries. These chemistries offer the advantage of decreased size (volume) and mass for a given power and energy requirement than otherwise available with conventional chemistries. For that reason, batteries employing chemistries like lithium-ion or lithium cobalt oxide chemistries have been incorporated into automotive and aerospace applications. However, some of these high energy chemistries are reported to have upper operating temperature limits above which the risk of thermal runaway increases.
Thermal runaway is a condition wherein the exothermic reaction associated supplying power accelerates beyond the capability to manage the generated heat. Increasing temperature leads to increased power output, leading in turn to further temperature increase. For that reason, vehicles may include features such as external passive or active cooling which function to keep electrical storage devices, e.g. batteries, below the temperature at which thermal runaway occurs. Conventional cooling systems may further include a capability to cool the power storage device once the battery is above its thermal runaway temperature.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for a thermal management system that allows for improved power source cooling. There also remains a need in the art for an improved thermal management system that cools of power sources approaching and/or above temperatures at which thermal runaway occurs. There further remains a need in the art for a thermal management system that is easy to make and use, such as by allowing access to the batteries for servicing. The present invention provides a solution for at least one of these problems.